Crushed or processed bulk material, such as stone aggregate and the like, is often stored in a hopper and later directed by means of a conveying system to a desired work station. The rate at which the material is delivered to the work station depends upon the particular operation; some operations requiring that the material be delivered at a fairly rapid rate while others require that the material be fed to the station at a very slow rate. Also, the speed with which a particular operation is carried out can vary so that material is required at different rates at different times. It is therefore desirable that any mechanism that is to be used to feed granular material or the like from a hopper to a conveyor be capable of delivering the material at rates which may be varied from a full flow rate to a dribble.
Mechanisms have been provided for varying the rate of discharge of material from a feeder and, while these mechanisms have some advantageous features, none of them have applied the principles of the present invention to accomplish effective, controlled discharge throughout a range of discharges, especially at the low discharge end of the range.
One prior art mechanism includes a variable speed drive having pulleys which are adjustable to vary the effective diameter of the drive sheave. Such a device is shown in the patent to Poynter, U.S. Pat. No. 3,236,381. Other drive mechanisms are disclosed in the patents to Franz, U.S. Pat. No. 1,089,633; to Carrier, U.S. Pat. No. 2,947,410; to Sinden, U.S. Pat. No. 3,099,349; to Brown, U.S. Pat. No. 3,547,252; to Mendoza, U.S. Pat. No. 3,567,012; to Scheffler, U.S. Pat. No. 3,945,513; to Zier et al., U.S. Pat. No. 3,901,380; and to Bertrand, U.S. Pat. No. 4,088,223.
The mechanism of the present invention features an eccentric drive unit adapted to reciprocate a feed pan on which material is disposed so that the material is discharged over the edge of the pan during its reciprocating movement. A novel control mechanism is operatively connected to the drive mechanism and provides means whereby the amount of reciprocation of the pan can be varied to control the amount of material discharged during each reciprocation.
An object of the present invention therefore is to provide an advantageous, effective, variable-throw drive mechanism for a feeder.